DE 196 53 722 A1 discloses a manual drive acting on both sides to produce a rotary movement. The device has a stepped switch mechanism that contains a fixing device that locks torque occurring on the output side. The stepped switch mechanism is arranged between a drive and an output element. The fixing device is formed as a loop spring brake and prevents the undesired displacement of the adjustment device, for example a seat back.
In order to achieve this fixing position a relatively complicated mechanism is required having a number of component parts that have to be fitted together in an expensive assembly process.